I know this is not what you’re asking for, but I’d instead advise you on not using email as your primary sales vehicle.

I also know it depends on the product you’re selling.

Most often than not, email is a big pile of mess for most people, so getting their attention is just really hard.

If you can, if it’s viable, go to their office, shake their hand and pitch the product face to face.

Too far? Call and schedule a meeting.

Anyone can send an email blast to thousands of contacts. Not many have the courage to just pick up the phone or see people face to face.

Sorry I couldn’t help! But I hope this is useful :)

that's system working as intended.

SPAM is officially described as UCE, "Unsolicited Commercial Emails". Your emails are both unsolicited and commercial, so people rightfully block it. I know I always click "report spam" when I see an unsolicited commercial email, not just to clean my inbox ("report spam" and "delete" are right next to each other), but to make sure sender's reputation takes a hit and fewer other people get spam email.